Owing to the characteristics of the liquid crystal display (hereinafter it is also referred to as the LCD) for the color display such as the thin shape, the light weight, the power consumption saving and the flickerless, the market thereof has rapidly been expanded mainly for the laptop type personal computers. Recently, as a part of such a display apparatus for the personal computers, demand for the monitors for the desktop type personal computers larger than the laptop type personal computers has been generated. Moreover, not only for the personal computer application, the LCD has been utilized also for the televisions, for which the cathode ray tube (CRT) has conventionally been the mainstream.
Here, as the problems peculiar to the LCD, its narrow visual angle issue can be presented. This is due to the light leakage generated from the pixels, which originally should display the black, in the case the LCD is observed from the oblique direction. Therefore, the contrast inversion is generated so that the correct display cannot be achieved. In view of the problem, a wide visual angle LCD without the light leakage even in the case the visual angle is increased in the black display pixels using the retardation layer has been studied.
For example, according to the liquid crystal display device of the vertical alignment mode, for improving the visual angle characteristics, as described in the Japanese Patent Application Laid Open (JP-A) No. 10-153802, a retardation layer having the optical axis perpendicular to the substrate with the negative birefringence anisotropy (negative C plate), and a retardation layer having the optical axis parallel to the substrate with the positive birefringence anisotropy (positive A plate) are used in a combination.
In the same manner, according to the liquid crystal display device of the horizontal alignment mode, by using a retardation layer having the optical axis perpendicular to the substrate with the positive birefringence anisotropy (positive C plate), and a retardation layer having the optical axis parallel to the substrate with the positive birefringence anisotropy (positive A plate), the optical compensation can be enabled. Since the optical compensation of the liquid crystal display device of the horizontal alignment mode is the optical compensation of the polarizing plates in the crossed Nicol state, this method can widely be adopted for the liquid crystal display device utilizing the polarizing plate in the crossed Nicol state.
Conventionally, as the retardation layer, except the positive C plate, a transparent polymer film with the stretching process applied has widely been adopted. Moreover, all the retardation layers can be produced also by aligning and fixing a liquid crystal material having the refractive index anisotropy with the certain regularity. In particular, as to the positive C plate, it cannot be produced by the stretching process of a polymer so that it can substantially be produced only by using the liquid crystal material.
Here, in the case of the optical compensation over the entire visual light range at a certain observation angle, a problem is involved in that the retardation amount required to the retardation layer differs depending on every wavelength. According to the optical compensation using the retardation layer, since the wavelength dependency of the retardation amount is determined by the characteristics of the material comprising the retardation layer, in general the optical design is provided with the green color, which has the highest visual sensitivity. In this case, since the accurate optical compensation cannot be realized for the red color and the blue color, if the visual angle is made larger in the black display state, the light leakage of the red color and the blue color becomes conspicuous so that a problem arises in that it is observed for the reddish purple color, or the like.
Here, for example in the JP-A No. 2003-315550, a retardation layer having the so-called inverse dispersion characteristics with the refractive index anisotropy on the longer wavelength side of the visual light range larger than the refractive index on the shorter wavelength side has been proposed. However, the retardation layer in the JP-A No. 2003-315550 is produced by aligning the polymer so that a retardation layer using the liquid crystal material having the inverse dispersion characteristics has never been developed.